Contents lists available at ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo Research paper Compaction, rock physics and rock properties of sandstones of the Stø Formation: Case study of five wells from the south-western Barents Sea, Norway Oluwakemi Yetunde Ogebule a,* , Jens Jahren a , Nazmul Haque Mondol a,b a Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, 0316, Oslo, Norway b Norwegian Geotechnical Institute (NGI), P.O. Box 3930, Ullevaal Stadion, 0806, Oslo, Norway ARTICLE INFO Keywords: Barents sea Compaction Exhumation Intergranular volume (IGV) Rock physics Permeability Porosity Velocity ABSTRACT Five wells containing Lower-Middle Jurassic sandstones of Stø Formation from the Hammerfest Basin (7120/ 9–1, 7121/7–1), the Ringvassøy-Loppa Fault Complex (7119/12–1, 7119/12–4) and the Troms-Finnmark Fault Complex (7019/1-1) in the Barents Sea area are considered in this study. The Stø Formation sandstones contain dominantly very fine-to medium-grained quartz arenites with occasional coarse-grained sandstone layers. Feldspathic and quartz wackes are also present. The effect of compaction and exhumation on reservoir properties (porosity and permeability) and seismic property (P-wave velocity) of these sandstones have been investigated. Source of quartz cement has also been investigated. Forty polished thin sections embedded in blue epoxy were studied using optical microscopy, scanning electron microscopy and cathodoluminiscence. Bulk mineralogy was also analysed using X-ray diffraction. The studied sandstones have experienced Cenozoic exhumation ranging between 820 and 1050 m. P-wave velocity is higher; porosities and permeabilities are lower in the western wells (7019/1-1, 7119/12–1 and 7119/ 12–4) compared to the eastern wells (7120/9–1 and 7121/7–1). Rock physics models and diagnostics show that the western wells are diagenetically more mature, stiffer, more compacted and more cemented than the eastern wells. These trends are attributed largely to difference in burial history from the east to the west and less to textural variations. Quartz cement is the most important authigenic mineral in these sandstones. Quartz cement in the western well (7119/12–1) is predominantly derived from clay-induced dissolution at macrostylolites whereas the eastern wells (7120/9–1 and 7121/7–1) are mostly sourced from clay-induced dissolution at grain contacts or microstylolites. While cementational porosity loss dominates in the western wells, compactional porosity loss dominates in the eastern wells. Compaction can reduce porosities down to 26% and this might be the reason for better porosity preservation and reservoir quality in the eastern wells than in the western wells. 1. Introduction The Norwegian Barents Sea area is a highly prospective hydro- carbon province. The Lower-Middle Jurassic Stø Formation is the most important reservoir rock in the area of study. This reservoir rock like every other rock has experienced its properties change continuously from deposition through burial and during uplift. These changes are referred to as compaction. Compaction is a term that describes porosity reduction and in- creased density and velocity during burial (Storvoll and Brevik, 2008). Compaction could either be mechanical where changes occur as a function of effective stress or chemical where changes are due to tem- perature and time (Bjørlykke, 2006). At shallow burial depth, porosity loss is mainly mechanical in siliciclastic rocks and is due to grain re- orientation, pseudo-plastic deformation of ductile grains and brittle grain fracturing (Bjørlykke et al., 1989; Bjørkum et al., 1998; Chuhan et al., 2002; Mondol et al., 2007; Fawad et al., 2011). At depositional surface, an intergranular volume (IGV) of about 40% is present in well sorted sands. At the onset of chemical compaction, IGV in sandstones usually vary between 25% and 30% and could be higher in well sorted quartz-rich sands (Rittenhouse, 1971; Houseknecht, 1987, 1988; Stone and Siever, 1996; Ramm, 1992; Paxton et al., 2002; Chuhan et al., 2003). At deeper burial, porosity loss is chemical in nature. Chemical compaction includes processes that involve dissolution of less stable minerals and precipitation of more thermodynamically stable minerals https://doi.org/10.1016/j.marpetgeo.2020.104448 Received 4 January 2017; Received in revised form 6 April 2020; Accepted 7 May 2020 * Corresponding author. E-mail address: o.y.ogebule@geo.uio.no (O.Y. Ogebule). Marine and Petroleum Geology 119 (2020) 104448 Available online 11 May 2020 0264-8172/ © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). T